1. Field of the Invention
The present invention relates to an exposure apparatus.
2. Description of the Related Art
In fabricating a semiconductor memory device, a flat panel display device such as a liquid crystal display device or a plasma display device, a printed circuit board, a filter and other elements using thin film technology, a photolithographic etching method for forming a fine pattern is used. The photolithographic etching method necessitates an exposure apparatus for transferring patterns of a reticle or a mask onto a photosensitive film formed on a substrate.
An example of this exposure apparatus is schematically illustrated in FIG. 1, and includes a reticle stage 18 on which a reticle 500 having a predetermined pattern drawn thereon or a mask is placed, and a plate stage 19 on which a substrate 600 where the pattern of the reticle 500 is to be formed is placed. An alignment optical system 21 for alignment of the reticle 500 is provided in the reticle stage 18.
Light emitted from a light source is directed to a dichroic mirror 12, and light having a specific wavelength is reflected from the dichroic mirror 12.
Light reflected from the dichroic mirror 12 passes through a filter 15 and a fly's eye lens 16 to become a point light source and is directed to a focusing lens 13 via a shutter 17 and a reflection mirror 14.
Light having passed through the focusing lens 13 is projected onto the reticle 500, and passes through a projection optical system 22 to be irradiated onto the substrate 600, thereby exposing a photosensitive film made of a photosensitive material and formed on the substrate 600 in a predetermined pattern.
An automatic focusing controller 23 is provided in the plate stage 19 so that the light having passed through the projection optical system 22 is accurately focused on the substrate 600.
When exposure is made using the above-described conventional exposure apparatus, the exposure pattern of a large-scale panel may be distorted and some parts of a substrate may not be exposed. Also, since the large-sized exposure apparatus is mounted on a light frame, the exposure apparatus may vibrate due to an externally applied minor shock, which impairs exposure reliability and stability.